To splash out on something proper, usually as a one-off treat. It’s spending a bit recklessly on purpose, knowing full well your bank app is about to tut at you. Can be anything from a fancy dinner to new trainers. Honestly, it’s retail therapy with your eyes wide open.
"I had a ‘just one little treat’ moment and splurged on a new laptop, then had to live off instant noodles till payday like a right muppet"